Not applicable.
1. Field of the Invention
The present invention relates to a reciprocating fluid pump, and more particularly relates to a check valve for use in a reciprocating fluid pump, and even more particularly relates to such a reciprocating fluid pump check valve used in an abrasive environment, for instance, a slurry pump.
2. Description of the Prior Art
Reciprocating fluid pumps are well known in the fluid industry. Many such pumps are categorized as reciprocating diaphragm, piston, bellows, etc. type, such pumps comprising a pair of opposed diaphragms, etc. fixed to opposite ends of a drive shaft that reciprocates the opposed diaphragms, etc. within respective pumping cavities to effect pumping of the fluid. Typically, such a fluid pump is actuated by pneumatic (air) pressure acting on one surface of the diaphragm, the opposite surface of the diaphragm exposed to the pumped fluid. Each diaphragm is positioned within a respective pumping cavity such that the diaphragm divides the cavity into a pneumatic chamber and a pumped-fluid chamber. The pumped-fluid chamber includes a first check valve at the xe2x80x9cfluid-inxe2x80x9d section of the pump and a second check valve at the xe2x80x9cfluid-outxe2x80x9d section of the pump. These check valves operate to ensure that fluid flows in only one direction, i.e., in the fluid-in section of the pump and out the fluid-out section of the pump.
Check valves can be typically flapper valves or ball valves. Ball-type check valves typically have a circular valve seat at one end of a more-or-less cylindrical ball chamber to which the ball valve element seats (seals) to prevent flow in the reverse direction (back-flow) through the check valve. The opposite end of the cylindrical ball chamber has no valve seat, but rather is designed to support the ball valve element away from the end of the chamber in order to permit fluid flow around the ball valve element and through the check valve in the forward direction.
Ball-type check valves have various mechanisms for seating the ball valve element against the valve seat. Typical of these are (1) a spring that urges the ball valve element toward the valve seat, (2) gravity that urges the ball valve element downwardly toward the valve seat, (3) the ball valve element being constructed of a lesser density material than that of the fluid through the check valve so that upward flow of fluid through the valve xe2x80x9cfloatsxe2x80x9d the ball valve element against the valve seat, etc.
The check valve of the present invention is a ball-type valve that incorporates multiple annular valve seats of progressively smaller diameters for the specific purpose of providing a series of effective valve seats as the larger annular valve seats progressively deteriorate, and as the ball valve element wears away (decreases in diameter) from use, for example, as abrasive slurry material is pumped through the check valves and through the fluid pump. Each of the annular valve seats (34, 38) comprises a flexible or otherwise deformable annular lip defined by a cylindrical section having an annular groove (36, 40) formed therein slightly outboard of the cylindrical section, such that the cylindrical section may deform slightly outwardly into the annular groove, thereby effecting an improved functional sealing engagement with the ball valve element as the tip of the cylindrical section deforms outwardly into the annular groove.
As abrasive slurry material is pumped through the fluid pump and through the check valve, the first annular valve seat (34) defined by the first cylindrical section and surrounding first annular groove (36) deteriorates and the ball valve element (24) wears away, due to the flow of abrasive slurry through the check valve, causing the first annular valve seat to erode away and causing the ball valve element to wear down (decrease in diameter). The first annular valve seat slowly deteriorates, and therefore increases in diameter, and the ball valve element slowly wears away, decreasing in diameter, to the point where they become no longer effective as a fluid seal. The worn ball valve element then engages a second annular valve seat (38), of the same configuration as the first annular valve seat (34), only necessarily of a smaller diameter than that of the first annular valve seat, and effects a seal therebetween. The combination of the increase in diameter of the first annular valve seat (34) and decrease in diameter in the ball valve element (24) permits the ball valve element to drop further toward the second annular valve seat (38), thereby causing the ball valve element to engage the second annular valve seat. The second annular valve seat (38) is spaced apart from the first annular valve seat (34) a distance to permit the second valve seat to seal with the ball valve element upon the occurrence of the first valve seat wearing and deforming a sufficient and pre-determined amount.
The process then repeats itself. Specifically, the second annular valve seat (38) is identical to but smaller than the first annular valve seat (34), comprising a cylindrical section defined by a second annular groove (40) immediately outboard of the cylindrical section, such that the tip of the cylindrical section is permitted to deform outwardly as it is engaged by the ball valve element, thereby creating the seal against the ball valve element and second annular valve seat. As the abrasive slurry material is pumped through the fluid pump and through the check valve, the second annular valve seat defined by the second cylindrical section and surrounding annular groove deteriorates and the ball valve element continues to further wear away from the flow of abrasive slurry, causing the second annular valve seat to erode away and the ball valve element to further wear down. The second annular valve seat slowly deteriorates, and therefore increases in diameter, and the ball valve element further wears away, further decreasing in diameter, to the point where they become no longer effective as a fluid seal. The worn ball valve element then engages a third annular valve seat (not shown in the drawings), of the same configuration as the first and second annular valve seat, thereby causing the ball valve element to engage the third annular valve seat as the second annular valve seat and ball valve element continue to deteriorate.